Phase-Shifted Full-Bridge Converter with Current Injection
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Solution Overview
Problem
Traditional phase-shifted full-bridge power converter topologies fail to achieve soft switching across secondary rectifiers, leading to voltage spikes and ringing, which negatively impact efficiency and require additional protective apparatus, and existing solutions either limit operation to discrete conditions or increase converter size and cost.
Innovation Solution
The implementation of a true soft switching phase-shifted full-bridge topology that ensures zero voltage switching across all switching elements by using a combination of magnetizing current and current injection to discharge parasitic capacitances, regardless of leakage inductance, allowing operation in continuous mode with high efficiency and reduced leakage inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional phase-shifted full-bridge topology is used, then the converter can operate with simple structure, but voltage spikes and ringing occur across secondary rectifiers leading to reduced efficiency
Solution Approach 1:
The patent applies preliminary action by initiating current injection before the secondary rectifier turns off. The controller detects when the secondary rectifier current approaches zero and activates the injection switch to inject current through the injection winding, ensuring the rectifier current reaches zero exactly at the desired moment for soft switching, thereby eliminating voltage spikes without requiring complex snubber circuits
Solution Approach 2:
The patent introduces an intermediary element - the injection winding coupled to the secondary winding through a magnetic coupling means. This injection winding acts as a mediator that transfers current from the primary side to the secondary side at a controlled rate, enabling precise control of the secondary rectifier current to achieve zero-current turn-off without directly modifying the rectifier circuit
2Reliability
If leakage inductance is increased to achieve soft switching, then zero voltage switching is obtained across primary switchers, but converter size and cost increase
Solution Approach 1:
The patent extracts the soft switching function from the leakage inductance element. Instead of relying on the transformer's leakage inductance to provide soft switching, the invention separates this function by using a dedicated injection winding with controllable current injection. This allows the main transformer to be designed with minimal leakage inductance for high efficiency while the injection mechanism provides the necessary soft switching control
Solution Approach 2:
The patent applies parameter changes by dynamically controlling the injection current magnitude and timing through the injection switch. The controller adjusts the injection current parameter to match the load conditions, enabling soft switching across a wide operating range without requiring fixed high leakage inductance values that would increase converter size
3Reliability
If additional snubbers are added to protect from voltage spikes, then reliability improves, but device complexity and cost increase
Solution Approach 1:
The patent implements self-service by using the magnetizing current and injection current to automatically discharge the parasitic capacitance across the primary switchers. The controller monitors the switching state and activates current injection when needed, allowing the converter to self-regulate and eliminate voltage spikes without requiring external snubber circuits or additional protective components
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach eliminates voltage spikes and ringing across secondary rectifiers, enabling efficient operation across various loading conditions and input voltages without the need for additional snubbers, and achieves high efficiency even with low or zero leakage inductance, suitable for high-power applications.
Implementation Method 1
using the energy in the leakage inductance to discharge the parasitic capacitance reflected across the primary switchers
Implementation Method 2
reflected through the transformer in the primary side
Data Source
AI summary
Methods for operation of a phase-shifted full-bridge topology power converter in a true soft-switching mode, regardless of the value of the leakage inductance of the converter. To achieve this, a process of discharge of the parasitic capacitances across the switching elements from a part of the resonant leg starts after the entire, total energy in the leakage inductance is used, and the voltage across the primary switching elements reaches the specific lower level.